Heated Oxygen Sensors

The Heated Oxygen Sensors are mounted in the exhaust system where they can monitor the oxygen content of the exhaust gas stream. The oxygen present in the exhaust gas reacts with the sensor to produce a voltage output. This voltage should constantly fluctuate from approximately 100 mV (high oxygen content = lean mixture) to 900 mV (low oxygen content = rich mixture). The heated oxygen sensor voltage can be monitored with a scan tool. By monitoring the voltage output of the oxygen sensor, the PCM calculates the fuel pulse width command to give to the injectors (lean mixture/low HO2S voltage = rich command, rich mixture/high HO2S voltage = lean command).

The PCM sets the following DTCs when the PCM detects an HO2S signal circuit that is low:
^ DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1.
^ DTC P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1.
^ DTC P0137 HO2S Circuit Low Voltage Bank 1 Sensor 2.
^ DTC P0157 HO2S Circuit Low Voltage Bank 2 Sensor 2.

The PCM sets the following DTCs when the PCM detects an HO2S signal circuit that is high:
^ DTC P0132 HO2S Circuit High Voltage Bank 1 Sensor 1.
^ DTC P0152 HO2S Circuit High Voltage Bank 2 Sensor 1.
^ DTC P0138 HO2S Circuit High Voltage Bank 1 Sensor 2.
^ DTC P0158 HO2S Circuit High Voltage Bank 2 Sensor 2.

The PCM sets the following DTCs when the PCM detects no HO2S activity:
^ DTC P0134 HO2S Insufficient Activity Bank 1 Sensor 1.
^ DTC P0154 HO2S Insufficient Activity Bank 2 Sensor 1.
^ DTC P0140 HO2S Insufficient Activity Bank 1 Sensor 2.
^ DTC P0160 HO2S Insufficient Activity Bank 2 Sensor 2.

A fault in the heated oxygen sensor heater element or its ignition feed or ground results in an increase in time to Closed Loop fuel control. This may cause increased emissions, especially at start-up. The following DTCs set when the PCM detects a malfunction in the HO2S heater circuits:
^ DTC P0135 HO2S Heater Circuit Bank 1 Sensor 1.
^ DTC P0155 HO2S Heater Circuit Bank 2 Sensor 1.
^ DTC P0141 HO2S Heater Circuit Bank 1 Sensor 2.
^ DTC P0161 HO2S Heater Circuit Bank 2 Sensor 2.

The PCM also has the ability to detect the following HO2S problems:
^ HO2S response
^ Switching
^ Transition time
^ Incorrect ratio voltages

The PCM stores a DTC that indicates degraded HO2S performance if any of the above is detected.